Phil 8.15.16

Still thinking about genetic co-evolution, particularly as demonstrated in sexual selection. In S.S., we have a group that can develop extreme, ‘useless’ and even objectively dangerous traits as genetic conversation with in a group. Birds provide several examples, ranging from peacocks to the Resplendent quetzal. And I think I may have found a paper that proposes some useful models: Models of speciation by sexual selection on polygenic traits. So Group Polarization == Speciation???

From the above paper: “The evolution of mating preferences may be self-reinforcing because, once started, females are selecting not only for more extreme males but also indirectly, through the genetic correlation, for a higher intensity of mating preferences. Fisher (3) stated that the result of this positive feedback could be a “runaway process,” in which a male trait and female preferences for it both increase geometrically or exponentially with time until finally checked by severe counterselection. “

And more: “In a finite population, random genetic drift in female mating preferences produces random selective forces on males, which in turn affect mating preferences through the genetic correlation between the traits. When the line of equilibria created by genetic variance in mating preferences is unstable, random genetic drift could trigger a runaway process of sexual selection. Even when the line of equilibria is stable, evolution along it can occur rapidly through the interaction of random genetic drift with natural and sexual selection because populations starting from the same point may drift to different sides of the line of equilibria and be selected in opposing directions“